package com.duan.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

//操作数据库的公共类
public class baseDao {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    static {
        Properties properties = new Properties();
        //通过类加载器读取对应的资源
        InputStream is = baseDao.class.getClassLoader().getResourceAsStream("db.properties");

        try{
            properties.load(is);
        }catch (IOException e){
            e.printStackTrace();
        }

        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        username = properties.getProperty("user");
        password = properties.getProperty("password");
    }

    //获取数据库链接
    public static Connection getConnection(){
        Connection connection = null;
        try{
            Class.forName(driver); //得到数据库的连接对象。properties中的：driver=com.mysql.jdbc.Driver
            connection = DriverManager.getConnection(url, username, password);
        }catch (Exception e){
            e.printStackTrace();
        }

        return connection;
    }

    //编写查询公共类
    public static ResultSet execute(Connection connection, String sql, Object []params, ResultSet resultSet, PreparedStatement preparedStatement) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);

        for(int i = 0; i < params.length; i++){
            //setObject，占位符从1开始，但是我们的数组是从0开始
            preparedStatement.setObject(i+1, params[i]);
        }

        resultSet = preparedStatement.executeQuery();
        return resultSet;
    }

    //编写增删改查公共方法
    public static int execute(Connection connection, String sql, Object []params, PreparedStatement preparedStatement) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);

        for(int i = 0; i < params.length; i++){
            //setObject，占位符从1开始，但是我们的数组是从0开始
            preparedStatement.setObject(i+1, params[i]);
        }

        int updateRows = preparedStatement.executeUpdate();

        return updateRows;
    }


    //释放资源
    public static boolean closeResource(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet){
        boolean flag = true;

        if(resultSet != null){
            try{
                resultSet.close();
                //GC回收
                resultSet  = null;
            }catch (SQLException e){
                e.printStackTrace();
                flag = false;
            }
        }

        if(preparedStatement != null){
            try{
                preparedStatement.close();
                //GC回收
                preparedStatement = null;
            }catch (SQLException e){
                e.printStackTrace();
                flag = false;
            }
        }

        if(connection != null){
            try{
                connection.close();
                //GC回收
                connection = null;
            }catch (SQLException e){
                e.printStackTrace();
                flag = false;
            }
        }

        return flag;
    }
}
